A pushrod lock is known from DE 35 05 379 C1. The lock connected via a pushrod with a center lock. This pushrod therefore connects the elements of the two locks. In this way it is possible to connect a door with the locking plate on the door frame not only in the center, but also in the area of its corners. In the process of closing the door, the latches are pushed in via the locking plate, so that the door can take up its locked position. For opening the door, the latch of the center lock is actuated by means of a latch key or a lock cylinder and retracted, wherein the movement is transferred to the latch of the pushrod lock via the pushrod, so that this latch is also retracted. It is disadvantageous in this connection that the pushrod is always also activated in the course of the insertion movement of the latch. This leads to stiff movements of the latch and malfunctions.
A mortise lock with a latch bolt is known from EP 431 369 A2. Besides the job of a conventional bolt, this latch bolt has the job of additionally locking the door, which is accomplished in that after closing the door the latch bolt changes automatically from a latch position into a lock position, in which it is extended away farther from the mortise lock than in the latch position and because of this extends deeply into the locking plate in the door frame. As a rule, such a latch bolt can no longer be pushed back by the insertion of a tool in the slit between the door and the door frame. A door with such a latch bolt is automatically locked after closing.
A locking device of the type mentioned at the outset is also known from DE 296 05 517 U1 wherein, however, there is the danger that in case of a warped door the spring-loaded latch bolt of the additional lock casing possibly no longer completely enters into the locking plate of the door panel frame and instead is jammed against the locking plate.